The validity of X-ray CT in the functional diagnosis of several cardiovascular diseases was evaluated. CT was useful for assessing the amount and the characteristics of intrapericardial fluid, and it was also useful for the diagnosis of cardiac tamponade and constrictive pericarditis. A dynamic scan was found to be useful for determining the location, direction and the magnitude of intracardiac shunts, and for differentiating the true lumen from the false lumen in dissecting aortic aneurysms. As direct evidence of myocardial infarction, a filling defect in the infarcted area and late enhancement of the same area on delayed scan were noted. Regional wall motion abnormalities could be demonstrated by ECG gated CT, and other findings such as myocardial thinning, ventricular aneurysm and mural thrombi in the infarcted area were documented.